With recent diffusion of smartphones and tablet terminals, touch panels are drawing attention. One of the problems of the touch panels is the deterioration of the appearance of terminals due to the visibility of indium tin oxide (hereinafter, referred to as “ITO”) pattern used in the sensor formation, that is, the problem of the ITO pattern visibility. Further, with a growing demand for a lighter weight and thinner terminals in recent years, a type of touch panel has been proposed, for example, in which the number of glasses used is reduced by forming a sensor on the back surface side of the cover glass (Patent Document 1). However, in this type of touch panel, referred to as a cover glass integrated type, the distance from the outermost surface of the terminal to the ITO pattern becomes shorter, compared to that of a conventional sensor glass/cover glass separated type, making the problem of the ITO pattern visibility more pronounced.
As the representative technique to reduce the ITO pattern visibility in liquid crystal display devices, a technique has been developed in which an insulating thin layer is formed on the upper part or the lower part of an ITO layer to reduce the interface reflection (Patent Documents 2 to 4). In addition, as the technique to reduce the ITO pattern visibility in touch panels, a technique has been developed in which a thin layer composed of Nb2O3 and SiO2 is disposed as an undercoat layer or a topcoat layer (Patent Documents 5 and 6).